In the assembly of goods, the performance of services and in a variety of other areas, the use of corded, hand-operated tools is often required. In the assembly of many consumer and industrial products, workers are often required to utilize hand-held tools powered by electrical energy, air pressure, etc., in order to accomplish the specific assembly operation. In other professional service areas, such as occupied by surgeons, dentists, technicians, assistants, etc., corded power tools are also required to perform operations such as sawing, cleaning, drilling, suctioning, etc. in order to provide the treatment necessary to a patient. Many other fields of endeavor require the use of corded, hand-held power tools.
It has been found that in many instances the strain on the muscles and joints of an operator is not due solely to the weight of the power tool itself, but due to the weight of the cord attached to the power tool. This is especially the case where operators repeatedly utilize corded equipment over extended periods of time. While the corded tool itself can usually be held to balance the weight thereof in the operator's hand, this is not always true with the cord which dangles from the tool. To that end, significant advances have been made to ergonomically design hand-held tools so that the weight of the tool is well-balanced, the hand grip conforms closely to the shape of a human hand, and vibrations are reduced. This has the potential of reducing injuries that may occur over a period of time as a result of repeated trauma or exposure to strain on a worker's fingers, hand or arm. Such type of injuries are known as cumulative trauma disorders (CDTs). Such type of disorders are also referred to as repetitive strain injuries, repetitive motion disorders, over use syndrome, musculoskeletal disorders and work-related disorders. The risk factors attendant with the use of corded hand-held tools is generally related to vibration, repetition and mechanical stress.
Muscle and joint disorders caused by the weight of the cord have not been addressed in any substantial manner. Different from the hand-held tool itself, the cord can present different amounts of pressure or strain, as a function of the amount of cord dangling from the tool and otherwise unsupported. For example, if a portion of the cord from the tool lies on the floor, bench or table, then the higher the tool is elevated for use, more of the cord requires support and represents added weight that must be overcome by the hand, wrist or arm muscles of the operator. In order to circumvent some of these problems, it is known to suspend the cord from the ceiling and to support portions of the cord by springs, and the like. While these techniques provide some degree of assistance, certain situations dictate for a variety of reasons that the cords cannot be suspended from above.
U.S. Pat. No. 1,164,928 by Corcoran discloses a corded hand-held iron, where the cord is plugged into an outlet located at a position above the operator. In order to reduce the weight of the cord, an arm band is utilized, with a loop through which the cord is suspended. Although this concept appears to reduce the effective weight of the cord that must be supported by the person's arm, the cord is nevertheless unconstrained in the loop and can become unbalanced in terms of weight. In U.S. Pat. No. 3,809,349 by Baedke, an arm band and roller arrangement is utilized to engage the cord to facilitate the travel of the cord through the support in correspondence with the movements of the operator's arm. Although the cord is allowed to easily slide back and forth on the arm band roller, there is no way of controlling the amount of cord which the worker's arm must support. U.S. Pat. No. 2,261,046 by Anderson describes an electrical appliance cord holder that forces the cord against the muscles of the worker's arm to thereby prevent movement of the cord in either direction.
From the foregoing, it can be seen that a need exists for a cord strain relief that can control the weight of the cord pulling on the hand-hold tool to thereby control the stress placed on the operator's fingers and wrist. Another need exists for a cord strain relief that is adjustable as to the amount of cord that is suspended and thus supported by the tool. Yet another need exists for a cord strain relief that allows only a desired amount of cord to be suspended and supported by the tool.